• Korean Journal of Fisheries and Aquatic Sciences
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• v.16 no.2
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• pp.88-96
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• 1983

The effect of lowering water activity of various humectants has been reported in the previous papers. In this study, that effect of humectants used in combination with each other was discussed. Additionally, the Aw measurements were also compared to the predicted values of Aw derived from the equation of Raoult's law and the linear slope method by Sloan and Labuza. Each mixed humectant was thought to be salted-out by the other, and thus Aw values were observed to be somewhat lower as the result in all model preparations. The effect of lowering water activity by NaCl was the highest, and the efficiency of reduction of Aw was decreased in the order of NaCl, sodium lactate, glycerin, propylene glycol and sorbitol when each of them was combinated with other humectants. Aw values calculated by the equation of Raoult's law were not agreed so well to the measured Aw, so it was likely not to be the useful method for predicting Aw values in mixed humectants to far as they have showed higher ability for lowering Aw in the previous papers. The equations of prediction were derived from Aw values to be measured actually in the model Kamaboko.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.11
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• pp.3-10
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• 2014

Direct conversion receiver(DCR) gets noticed for integration and cost reduction of wireless communication systems instead of the heterodyne receiver which uses complex filter. But DCR has several factors in performance degradation. One of them is I/Q imbalance phenomenon, that is amplitude and phase mismatch between real and imaginary part of receiver. Accordingly, researches are being carried to improve the I/Q imbalance problem. However, the tendency of the broaden bandwidth of communication systems, low pass filter(LPF) mismatch problem affects severely in I/Q mismatch phenomenon at the DCR. To study this problem, we generated 10MHz broadband signal and shifted it ${\pm}8MHz$ from the center frequency. The signal is affected by LPF mismatch and it appears as frequency selective distortion. Thus, LPF mismatch model is added to I/Q imbalance model which conventionally dealt with amplitude and phase mismatches. In addition, we proposed the compensation method for each factors of mismatch. As the simulation results, the proposed I/Q mismatch compensator resolves the frequency selective distortion which occurred by the existing LPF mismatch.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.14 no.1
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• pp.77-84
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• 2015

In 2011, greenhouse gas emissions of transport sector were 85.04 million $tonCO_2eq$ and road emissions accounted for 95% of total emissions in the transport sector. There are few innovative technologies to reduce greenhouse gas emissions aside from eco-driving education and public relation program. Therefore, this paper focused on analyzing optimal acceleration by certain road grades and suggested fuel-efficient driving method for various uphill sections. Scenarios were established by driving modes. Speed profiles were generated by scenarios and speed variations. Each speed profile applied to Comprehensive Modal Emission Model and then each fuel consumption was estimated. Driving mode and speed variation that minimized fuel consumption were driven according to grade percent and uphill distance. When driving in the eco-friendly mode of the driving and speed variation, reduction rate of fuel consumption was evaluated by comparison between eco-driving and cruise control mode. When a vehicle drove under eco-driving mode at 100kph, 90kph and 80kph on uphill road, fuel consumptions were reduced by 33.9%, 30.8% and 5.3%, respectively.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.4
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• pp.276-282
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• 2013

The reclaimed water has been highlighted as a representative alternative to solve the lacking water resources. This study examined the reduction of residual free chlorine by temperature (5, 15, $25^{\circ}C$) and initial injection concentration (1, 2, 4, 6 mg/L) in the reclaimed water and carried out propose on the calculating method of the optimal chlorine dosage. As the reclaimed water showed a very fast reaction with chlorine at the intial time comparing to that of drinking water, the existing general first-order decay model ($C_t=C_o(e^{-k_bt})$) was not suitable for use. Accordingly, the reduction of residual free chlorine could be estimated in a more accurate way as a result of applying the exponential first-order decay model ($C_t=a+b(e^{-k_bt})$). ($r^2$=0.872~0.988). As a result of calculating the bulk decay constant, it showed the highest result at 653 $day^{-1}$ under the condition of 1 mg/L, $25^{\circ}C$ for the initial injection whereas it showed the lowest result at 3.42 $day^{-1}$ under the condition of 6 mg/L, $5^{\circ}C$ for the initial injection. The bulk decay constant tends to increase as temperature increases, whereas the bulk decay constant tends to decrease as the initial injection concentration increases. More accurate calculation for optimal chlorine dosage could be done by using the experimental results for 30~5,040 min, after the entire response time is classified into 0~30 min and 30~5,040 min to calculate the optimal chlorine dosage. In addition, as a result of calculating the optimal chlorine dosage by temperature, the relationships of initial chlorine demand (y) by temperature (x) could be obtained such as y=1.409+0.450x to maintain 0.2 mg/L of residual free chlorine at the time after 4 hours from the chlorine injection.

• Journal of Korean Society of Transportation
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• v.20 no.1
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• pp.77-90
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• 2002

Network expansion has been an inevitable method for most traffic equilibrium assignments to consider intersection movements such as intersection delays. The drawback of network expansion is that because it dramatically increases network sizes to emulate possible directional movements as corresponding links, not only is complexities for building network amplified, but computational performance is shrunk. This paper Proposes a new variational inequality formulation for a user-optimal traffic equilibrium assignment model to explicitly consider directional delays without building expanded network structures. In the formulation, directional delay functions are directly embedded into the objective function, thus any modification of networks is not required. By applying a vine-based shortest Path algorithm into the diagonalization algorithm to solve the problem, it is additionally demonstrated that various loop-related movements such as U-Turn, P-Turn, etc., which are frequently witnessed near urban intersections, can also be imitated by blocking some turning movements of intersections. The proposed formulation expects to augment computational performance through reduction of network-building complexities.

• Journal of Korean Society of Environmental Engineers
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• v.22 no.12
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• pp.2175-2185
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• 2000

Respiration rate should be a reasonable state variable for the activated sludge and could be used to simulate the performance of the activated sludge process. Toxic materials are classified into three groups, competitive, noncompetitive and uncompetitive. They increase/decrease the half saturation coefficient or specific growth rate. that means decreasing of the substrate removal capacity. In this research, a pilot-scale activated sludge process was operated under extended aeration method, and a representative noncompetitive inhibitor, acidic wastewater was applied to establish a respirometry-based toxicity model. Using this model. the correlation coefficient between measured and calculated respiration rate was 0.96 when acidic wastewater(pH 3.9~5.5) was introduced continuously to the aeration tank. Even though respiration rate was decreased by toxic effect of acidic wastewater, effluent substrate concentration represented to COD was deteriorated just a little bit. It might be caused by the low ratio of readily biodegradable substrate in the input substrate. Reduction of respiration rate by decreasing of input substrate concentration was much lower than that by acidic wastewater, and hence it was estimated that the possibility of false toxic alarm caused by decreasing of substrate concentration should be low.

• Journal of the Korean Society of Marine Environment & Safety
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• v.22 no.5
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• pp.521-526
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• 2016

Sediment dredging can permanently remove pollutants from an aquatic ecosystem, which is considered an effective approach to aquatic ecosystem restoration. In this study, we quantified the effects of sediment dredging on water quality in Masan Bay by calculation of oxygen demanding rate. We applied ecosystem model including water and sediment quality module in Masan Bay. The results showed that the increase of calculated oxygen demanding rate is significant due to sediment dredging of both inner part and outer part of Masan Bay. On the other hand, the increase is gradual due to decrease of anthropogenic load. It meant sediment dredging can improve water quality of Masan Bay more. Using correlation equation between oxygen demanding rate and sediment oxygen demand, we calculated that the area of sediment dredging which is equal to the effects of 10 % reduction of anthropogenic load. It is $1.68km^2$ in inner part and $3.15km^2$ in outer part of the Masan Bay. This Meant that to improve water quality of Masan Bay, sediment dredging in inner part is efficient method.

• Journal of the Korea Concrete Institute
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• v.15 no.2
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• pp.314-322
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• 2003

Pipe cooling method is widely used for reduction of hydration heat and control of cracking in mass concrete structures. However, in order to effectively apply pipe cooling systems to concrete structures, the coefficient of flow convection relating the thermal transfer between inner stream of pipe and concrete must be estimated. In this study, a device measuring the coefficient of flow convection was developed. Since a variation of thermal distribution caused by pipe cooling has a direct effect on internal forced flows, the developed testing device is based on the internal forced flow concept. Influencing factors on the coefficient of flow convection are mainly flow velocity, pipe diameter and thickness, and pipe material. Using experimental results from the developed device, the coefficient of flow convection was calculated. Finally, a general prediction model was proposed by theoretical procedures. The proposed prediction model is able to estimate the coefficient of flow convection with flow velocity and material properties of pipe. From comparison with experimental results, the coefficient of flow convection by this model was well agreed with those by experimental results.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.5
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• pp.1039-1049
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• 2015

The inflow estimation at large multipurpose dam reservoir is carried out by considering the water balance among the discharge, the storage change during unit time interval obtained from the observed water level near dam structure and area-volume curve. This method can be ideal for level pool reservoir but include potential errors when the inflow is influenced by the water level slope due to backwater effects from upstream flood inflows and strong wind induced by typhoon. In addition, the other uncertainties arisen from the storage reduction due to sedimentation after the dam construction and water level noise due to mechanical vibration transmitted from the electric power generator. These uncertainties impedes the accurate hydraulic inflow measurement requiring exquisite hydrometric data arrangement for reservoir waterbody. In this study, the distributed hydrologic model using UBC-3P boundary setting was applied and its feasibility was evaluated. Finally, the modeling performance has been verified since the calculated determination coefficient has been in between 0.96 to 0.99 after comparing with observed peak inflow and total inflow at Namgang dam reservoir.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.4
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• pp.165-174
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• 2011

This research aims at the optimal constitution of sensors required to identify the structural shortcoming of roller-coaster. In this research we analyzed the dynamic characteristics of roller-coaster by three dimensional FE modelling, decided on the appropriate location and number of sensors through optimal transducer theory, abstracted the mathematical value of modal features before and after damage on the basis of optimally placed and numbered sensors. and then presented it as a primary information about the basic structure which would be applied to damage estimation. As a target structure, the roller-coater at Seoul Children's Grand Park was chosen and built as a model reduced by one twentieth in size. In order to consider the Kinetics features particular to the roller-coaster structure, we made an exact three-dimensional FE modelling for the model structure by means of Spline function. As for the proper location and number of sensors, it was done by applying EIM and EOT. We also estimated the damage from the combination of strength, flexibility, and model corelation after abstracting the value of modal features. Finally the optimal transducer theory presented here in this research was proved to be valid, and the structural damage was well identified through changes in strength and flexibility. As a result, we were able to present the optimal constitution of sensors needed for the analysis of dynamic characteristics and the development of techniques in dynamic characteristics, which would ultimately contribute to the development of health monitoring for roller-coaster.